Stuttering is a speech-disfluency problem that can have significant developmental and social impacts upon stuttering individuals. Stuttering can include repetitions of parts of words and/or whole words, prolongation of sounds, interjections of sounds or words, and unduly prolonged pauses.
Conventional stuttering treatment techniques typically focus on alerting the patient that stuttering is occurring and having the patient try to modify their breathing and/or speech patterns in an attempt to avoid stuttering. For instance, U.S. Pat. No. 4,020,567, entitled Method and Stuttering Therapy Apparatus, issued to Webster on May 3, 1977, discloses a system for helping individuals determine when they are stuttering. The system generates an electrical signal based on the person's speech and uses the signal to detect certain speech characteristics corresponding to stuttering. A first embodiment detects speech onset errors during the first 100 milliseconds of syllable pronunciation. In a second embodiment, stuttering is detected by evaluating the rate of change in the amplitude of the person's speech. An LED is illuminated to notify a system-user that stuttering is occurring. The system disclosed by Webster is intended for use by stutterers while they practice learning not to stutter.
U.S. Pat. No. 4,662,847, entitled Electronic Device and Method for the Treatment of Stuttering, issued to Blum on May 5, 1987, discloses an electronic device for treating stuttering. The device transmits electronic speech signals from a microphone to an earphone through two paths. One path is synchronous. The other path is asynchronous. During normal speech, the synchronous speech signal is transmitted to the earphone. At any pause in phonation, the device switches to the asynchronous path and transmits speech in a delayed auditory feedback mode until a change in the user's speech occurs.
U.S. Pat. No. 4,784,115, entitled Anti-Stuttering Device and Method, issued to Webster on Nov. 15, 1988, discloses an anti-stuttering device for enhancing speech fluency. The device detects vocal pulses generated by the opening and closing of a speaker's vocal folds. Electrical signals representative of the vocal pulses are transmitted to a receiver in the speaker's sealed ear canal where these signals are reproduced as audio pulses. The device reduces stuttering by providing an early indication of the characteristics of the speaker's voice via audio pulses. The audio pulses produce a resonant effect within the person's ear canal.
U.S. Pat. No. 5,794,203, entitled Biofeedback System for Speech Disorders, issued to Kehoe on Aug. 11, 1988, discloses a biofeedback system for speech disorders that detects disfluent speech and provides auditory feedback to enable fluent speech. The disfluent-speech detector can be either an electromyograph (EMG) or an electroglottograph (EGG). EMG is a system that measures the electrical activities of muscles through electrodes attached to a person's body. EGG records the opening and closing of a person's vocal folds. EGG's use two electrodes on a person's neck and measure the resistance between the electrodes. This resistance changes as the vocal folds open and close. An EGG can show the frequency of the vocal folds. This is the fundamental pitch of the user's voice, without the harmonics produced by the nasal cavities, mouth, and the like.
The system disclosed by Kehoe includes an electronic controller connected to an EMG and frequency-altered auditory feedback (FAF) circuit. The controller receives data from the EMG regarding muscle tension in the user's vocal cords, masseter, and/or other speech-production muscles. The controller then controls the pitch of the FAF circuit in accordance with the user's muscle tension. The user wears a headset with a microphone and headphones. Three EMG electrodes are taped onto the user's neck and/or jaw. When the user speaks fluently, with speech-production muscles relaxed, the user's hears his or her voice shifted lower in pitch. This downward-shifted pitch is relaxing and pleasant, sort of like hearing James Earl Jones speak. If the user's speech-production muscles are abnormally tense, however, the user will hear his or her voice shifted higher in pitch.
U.S. Pat. No. 6,231,500, entitled Electronic Anti-Stuttering Device Providing Auditory Feedback and Disfluency-Detecting Biofeedback, issued to Kehoe on May 15, 2001, is a continuation-in-part of U.S. Pat. No. 5,794,203. The Kehoe '500 patent discloses micropower impulse radar (MIR) as an alternative to EMG biofeedback for monitoring a user's muscle activity to detect disfluency. MIR is short-range radar, using commonly available microchips. Unlike other radar, MIR is small and inexpensive. A small sensor for monitoring laryngeal activity could be taped to a user's throat.
Conventional treatment techniques for treating stuttering typically do not use neurostimulation and/or drug delivery devices. These types of devices, however, are capable of treating a number of neurological disorders as well as symptoms of those disorders. In the context of neurostimulators, an electrical lead having one or more electrodes is typically implanted near a specific site in the brain of a patient. The lead is coupled to a signal generator that delivers electrical energy through the electrodes and creates an electrical field causing excitation of the nearby neurons to directly or indirectly treat the neurological disorder or symptoms of the disorder. In the context of a drug delivery system, a catheter coupled to a pump is implanted near a treatment site in the brain. Therapeutics are delivered to the treatment sites in predetermined dosages through the catheter.
In an article entitled Cessation of Stuttering After Bilateral Thalamic Infarction, A. Muroi et al. describe their observation of a patient who, after paramedian thalamic infarction, experienced cessation of stuttering. Neurology, vol. 53, pp. 890-91 (Sep. (1 of 2) 1999. In this article, A. Muroi et al. state that neuroimaging studies indicate that the occlusion of a single artery, the mesencephalic artery, have given rise to the infarction in the bilateral medial thalamus and rostral mesencephalic tegmentum. Further, in developmental stuttering, regional cerebral blood flow (rCBF) was observed as relatively increased in the medial and lateral prefrontal areas and in the orbital cortices, and also in the supplementary motor area (SMA) and the superior lateral premotor cortex. A. Muroi et al. then discuss a study by Nagafuchi and Takahashi in which a patient started to stutter after an infarct in the SMA. Another article, by Abe et al., describes a case of stuttering-like repetitive speech disorder after paramedian thalamomesencephalic infarction. Yet another article, by Andy and Bhatnager, reported that stuttering was elicited by destruction of the centromedian (CM) in one case; they also found that stimulation of the same region alleviated the acquired stuttering in another case. The work reported by Andy and Bhatnagar related only to adult onset, acquired stuttering, due to the presence of cortical or subcortical pathologies (related to a central pain syndrome), but did not involve the more common form of developmental stuttering. Further, there is no teaching in their work on the application of DBS or drug delivery for the chronic treatment of developmental stuttering as a disorder of the motor system. The dorsomedial (DM) nuclei and CM, which were involved in the case reported by A. Muroi et al., are reciprocally connected to the lateral prefrontal area and SMA, respectively. In light of these studies and the case reported by A. Muroi et al., the A. Muroi et al. article speculates that disordered function of the SMA-CM circuit or DM-lateral prefrontal cortex is responsible for developmental and acquired stuttering. Therefore, it may be possible to treat either developmental or acquired stuttering by stimulation or drug delivery of the neural circuits involved in stuttering.
Based on the foregoing, there is a need for stuttering-treatment techniques that use neural stimulation and/or drug delivery to target the neurological underpinnings of stuttering.